Haptoglobin is a plasma glycoprotein whose half time in the circulation of the rat is 19 days. When haptoglobin forms a complex with hemoglobin the complex is removed from circulation by the liver with a half time of only 4 minutes. Uptake of the complex by hepatocyte membranes is specifically blocked by glycopeptides derived from exhaustive pronase digests of haptoglobin and is inhibited by prior treatment of the complex with periodate or glycosidases. The haptoglobin complex does not inhibit uptake of asialoorosomucoid by hepatocyte membranes, nor vice versa. Since the above evidence suggests that uptake of the haptoglobin-hemoglobin complex by hepatocyte membranes is mediated by a carbohydrate specific membrane receptor different from that responsible for uptake asialo-orosomucoid, we have undertaken structural analysis of the carbohydrate portion of haptoglobin.